This invention relates to compound lever tools and, in particular, to compound lever tools in which the toggle mechanism is formed from sheet metal.
Various tools are known that employ multiple levers. Examples of early compound lever, cutting and crimping tools are disclosed in U.S. Pat. Nos. 146,829 and 147,850. A compound lever machine is one in which a train of levers are employed whereby force is transmitted from the arm of one lever to that of the next lever. One particular type of compound lever machine, which is particularly useful in amplifying forces for cutting and crimping, also employs a toggle joint to connect the actuating levers (which are typically integral with the tool handles). The toggle mechanism converts the large sweep of the handles into a shorter, more powerful clench at the jaws.
A problem with compound lever, toggled-jointed, tools is that over periods of use the actuating levers are deformed by the force of the toggle mechanism. When this happens the "action" becomes loose, making it difficult to part or shear smaller or harder objects. Traditionally, manufacturers of tools employing these mechanisms have resorted to massive, forged or cast actuating levers which can withstand deformation for reasonably long periods of time. However, most of these tools also have employed an adjustment to compensate for wear over long-term use. Examples of adjustable, compound lever tools can be found in U.S. Pat. Nos. 226,190, 2,527,496, 2,910,900, and 3,074,164.
Despite the cost, most manufacturers of compound lever tools have continued to rely upon forged steel or cast iron parts to form their actuating levers. Sheet metal stamped levers have replaced forged or cast parts only on tools which are not intended for long-term or heavy-duty use. Apparently, two reasons for this reluctance on the part of manufacturers are the perceived weakness of stamped parts and the inability to adjust sheet metal tools for wear.
The difficulty in adapting a sheet metal part to include a wear-adjusting mechanism resides in need to secure a lateral support between the toggle points. Typically, the adjustment mechanism in compound lever tools includes a screw which is threaded through the actuating lever and tightened over time. Because stamped parts are formed from thin sheets of metal, the strength of the adjustment mechanism and the range over which it can be adjusted are limited by the number of threads that can be formed within a hole in the sheet.
There exists a need for simpler, less expensive, adjustable cutting tools, for clipping metal bolts, bailing wire, sheet metal, as well as swaging or crimping ferrules, rings, clamps and the like. A compound lever, toggle-actuated cutting tool would satisfy a long-felt need in the industry, if it could be fabricated without resort to forged or cast actuating levers.